Thermoelectric materials can be used to turn waste heat into electricity or to provide refrigeration without any liquid coolants, and new study has found a way to nearly double the efficiency of a particular class of them that's made with organic semiconductors.

Share This

"Eventually this technology could allow us to create a flexible sheet -- think of Saran Wrap -- that can be rolled out or wrapped around a hot object to generate electricity or provide cooling," one of the researchers said.

Thermoelectric materials can be used to turn waste heat into electricity or to provide refrigeration without any liquid coolants, and a research team from the University of Michigan has found a way to nearly double the efficiency of a particular class of them that's made with organic semiconductors.

Related Articles

Organic semiconductors are carbon-rich compounds that are relatively cheap, abundant, lightweight and tough. But they haven't traditionally been considered candidate thermoelectric materials because they have been inefficient in carrying out the essential heat-to-electricity conversion process.

Today's most efficient thermoelectric materials are made of relatively rare inorganic semiconductors such as bismuth, tellurium and selenium that are expensive, brittle and often toxic. Still, they manage to convert heat into electricity more than four times as efficiently as the organic semiconductors created to date.

This greater efficiency is reflected in a metric known by researchers as the thermoelectric "figure of merit." This metric is approximately 1 near room temperature for state-of-the-art inorganic thermoelectric materials, but only 0.25 for organic semiconductors.

U-M researchers improved upon the state-of-the-art in organic semiconductors by nearly 70 percent, achieving a figure-of-merit of 0.42 in a compound known as PEDOT:PSS.

"That's about half as efficient as current inorganic semiconductors," said project leader Kevin Pipe, an associate professor of mechanical engineering as well as electrical engineering and computer science. Pipe is a co-author of a paper on the research published in Nature Materials on May 5, 2013.

PEDOT:PSS is a mixture of two polymers: the conjugated polymer PEDOT and the polyelectrolyte PSS. It has previously been used as a transparent electrode for devices such as organic LEDs and solar cells, as well as an antistatic agent for materials such as photographic films.

One of the ways scientists and engineers increase a material's capacity for conducting electricity is to add impurities to it in a process known as doping. When these added ingredients, called dopants, bond to the host material, they give it an electrical carrier. Each of these additional carriers enhances the material's electrical conductivity.

In PEDOT doped by PSS, however, only small fraction of the PSS molecules actually bond to the host PEDOT; the rest of the PSS molecules do not become ionized and are inactive. The researchers found that these excess PSS molecules dramatically inhibit both the electrical conductivity and thermoelectric performance of the material.

To improve its thermoelectric efficiency, the researchers restructured the material at the nanoscale. Pipe and his team figured out how to use certain solvents to remove some of these non-ionized PSS dopant molecules from the mixture, leading to large increases in both the electrical conductivity and the thermoelectric energy conversion efficiency.

This particular organic thermoelectric material would be effective at temperatures up to about 250 degrees Fahrenheit.

"Eventually this technology could allow us to create a flexible sheet -- think of Saran Wrap -- that can be rolled out or wrapped around a hot object to generate electricity or provide cooling," Pipe said.

University of Michigan. "Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity." ScienceDaily. ScienceDaily, 5 May 2013. <www.sciencedaily.com/releases/2013/05/130505145941.htm>.

University of Michigan. (2013, May 5). Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity. ScienceDaily. Retrieved March 3, 2015 from www.sciencedaily.com/releases/2013/05/130505145941.htm

University of Michigan. "Improving materials that convert heat to electricity and vice-versa: Turning waste heat into electricity." ScienceDaily. www.sciencedaily.com/releases/2013/05/130505145941.htm (accessed March 3, 2015).

More From ScienceDaily

More Matter & Energy News

Featured Research

Mar. 3, 2015 — Physicists have shown for the first time that electrons in graphene can be moved along a predefined path. This movement occurs entirely without loss and could provide a basis for numerous ... full story

Mar. 2, 2015 — For the first time, researchers have produced a 3-D image revealing part of the inner structure of an intact, infectious virus, using a unique X-ray laser. The virus, called Mimivirus, is in a ... full story

Mar. 2, 2015 — What do a human colon, septic tank, copper nanoparticles and zebrafish have in common? They were the key components used by researchers to study the impact copper nanoparticles, which are found in ... full story

Mar. 2, 2015 — A new simple tool developed by nanoengineers is opening the door to an era when anyone will be able to build sensors, anywhere, including physicians in the clinic, patients in their home and soldiers ... full story

Mar. 2, 2015 — A new twist on an old tool lets scientists use light to study and control matter with 1,000 times better resolution and precision than previously possible. Physicists have demonstrated "ponderomotive ... full story

Mar. 2, 2015 — Scientists report that they could observe experimentally the current flow along channels at the crystal surfaces of topological insulators. The channels are less than one nanometer wide and extend ... full story

Mar. 2, 2015 — Organic light emitting diodes (OLEDs), which are made from carbon-containing materials, have the potential to revolutionize future display technologies, making low-power displays so thin they'll wrap ... full story

Mar. 2, 2015 — A team of engineers is using magnetic force to design new and improved instruments for minimally invasive surgery. The use of magnetic actuation allows them to create tools that are more flexible and ... full story

Mar. 2, 2015 — The first semi-liquid, non-protein nucleating agent for automated protein crystallization trials is described. This 'smart material' is demonstrated to induce crystal growth and will provide a ... full story

Mar. 2, 2015 — What if one day, your computer, TV or smart phone could process data with light waves instead of an electrical current, making those devices faster, cheaper and more sustainable through less heat and ... full story

Featured Videos

Forensic Holodeck Creates 3D Crime Scenes

Reuters - Innovations Video Online (Mar. 3, 2015) — A holodeck is no longer the preserve of TV sci-fi classic Star Trek, thanks to researchers from the Institute of Forensic Medicine Zurich, who have created what they say is the first system in the world to visualise the 3D data of forensic scans. Jim Drury saw it in operation.
Video provided by Reuters

Solar Plane Passes New Test Ahead of World Tour

AFP (Mar. 2, 2015) — A solar-powered plane made a third successful test flight in the United Arab Emirates on Monday ahead of a planned round-the-world tour to promote alternative energy. Duration: 01:05
Video provided by AFP

Electric Hydrofoiling Watercraft Delivers Eco-Friendly Thrills

Reuters - Innovations Video Online (Mar. 2, 2015) — The Quadrofoil is a high-tech electric personal watercraft that its makers call a &apos;sports car for the water&apos;. When it hits 10 km/h, the Slovenian-engineered Quadrofoil is lifted above the water onto four wing-like hydrofoils where it &apos;flies&apos; above the surface with minimal water resistance. Matthew Stock reports.
Video provided by Reuters

Related Stories

July 15, 2014 — Thermoelectric devices, which convert heat to electricity and vice versa, can harness that wasted heat, and possibly provide the green tech energy efficiency that's needed for a sustainable ... full story

Feb. 20, 2014 — Scientists have found a creative way to radically improve thermoelectric materials, a finding that could one day lead to the development of improved solar panels, more energy-efficient cooling ... full story

Feb. 7, 2014 — Thermoelectric devices can cool materials by passing currents, or convert temperature differences into electric power. However, especially metallic structures have a very poor thermoelectric ... full story

Nov. 18, 2013 — Researchers want to make vehicles more efficient by using a resource most people aren't even aware of — the waste heat that results from the inherent inefficiency of engines when converting ... full story

Sep. 20, 2011 — More than 60 percent of the energy produced by cars, machines, and industry around the world is lost as waste heat -- an age-old problem -- but researchers have found a new way to make ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.